A. Field of Invention
This invention pertains to the art of elastomeric blends suitable for use in vehicle timing belts and other apparatuses that may be constructed with elastomeric compositions.
B. Description of the Related Art
Hydrogenated nitrile rubber and specifically, hydrogenated acrylonitrile butadiene rubber (HNBR) is becoming a preferred elastomer for use in vehicle timing belts. HNBR has high tensile strength, low permanent set, good abrasion resistance and high elasticity. Further, HNBR demonstrates good stability towards thermal aging and exhibits better properties at low temperatures compared to other suitable heat- and oil-resistant elastomers. Moreover, HNBR has good static and dynamic properties at operation temperatures and good retention of properties under continuous heat exposure. There are several other physical properties of HNBR that make it useful in automotive belt applications, including good viscoelastic properties in HNBR vulcanizates, a wide service temperature range from −40° C. to +150° C., resistance to fluids of various chemical compositions and excellent resistance to strongly alkaline and aggressive fluids.
Though HNBR exhibits excellent material properties for use in timing belts and other similar applications, HNBR is more expensive than conventionally used elastomers, including polychloroprene. Given the considerable expense of using elastomeric compositions containing high proportions of HNBR in timing belt and other similar applications, it is desirable to formulate blends of HNBR with lower cost diluents to reduce the overall cost of the elastomer component. It is known, for example, to blend HNBR with low-cost fillers, such as carbon black or clay. While such HNBR/filler blends address the issue of reduced cost, the material characteristics and physical properties of such blends suffer with increasing concentrations of filler. It is, therefore, desirable to prepare HNBR/diluent blends for use in timing-belt applications and other articles conventionally constructed with high HNBR concentrate elastomeric compounds, which have significantly reduced cost, without an unsuitable reduction in the desirable material properties of the resulting composition, including dynamic properties, abrasion resistance and tensile strength.